Boolean Modifier Issues (Engraving text on to a face)
You actually did what you wanted in the second picture, the old Text mesh is only still visible... you could delete it or hide it to see the results. Further notes on general good practice: After following Hikariztw's suggestion to join the text objects together first, which makes life way easier, you could try changing the solver to "Carve"... (in the modifier) takes a bit longer but is more accurate and less buggy most of the time. Also you could try to recalculate normals in edit mode for both objects (ctrl+N) –